保护输出过压的电路

在测试与测量应用中,必须为放大器、电源以及类似部件的输出端提供过压保护。实现这一任务的传统方式是在输出节点中增加串联电阻,并在电源线路或其它阈值电压上增加箝位二极管（参考文献1与图1）。这个电阻大大减小了电流输出的能力,以及低阻负载的输出电压摆幅。另外一种方案是用保险丝或其它限流器件,它优于这些箝位电路的高吸能能力。     

输出过压保护电路的设计思路

介绍了五种输出过压保护电路的设计思路,并根据每种方案的优缺点,分析如何在实际应用中选择最合适的输出过压保护电路。     

电压检测器及其应用电路(五)——“高电压”欠压、过压保护电路

<正> 近年来,电路的工作电压不断地降低,从5V降到3.6V、3.3V,甚至降到1.8V以下。但仍有一些电路工作电压为9V、12V,少数电路还有15～24V工作电压。电压检测器的检测电压大部分在6V以下,那么工作电压在6V以上时如何来检测呢?这里将工作电压大于6V的称之为“高电压”,本文将介绍提高电压检测器的检测电压的方法及“高电压”电路的欠压、过压保护电路。     

简单的家用电器过压保护电路

这种简单的过压保护电路可用于电视机以及其他家用电器避免因交流电源波动而使电器长期工作于过高电压下招臻的损坏。它采用运放μA741（IC1）作为检测电源过过压的比较器的两个输入端，其中反相端②通过R3和齐纳二极管ZD1取得稳定的5.1V作为比较基准，而波动电     

数字电压表过压保护电路

在使用数字电压表测量开关电源电路中的电压时，经常会由于人为疏忽出现意外情况。比如，开关电源电路中负责传输反馈信号的光电耦合器插反，造成主电压异常升高，并瞬间烧毁电压表。本文设计的数字电压表过压保护电路，巧妙地解决了烧表难题，实际使用情况表明，这种电路可靠性高、制作成本低。     

过压保护电路

本文讨论如何针对过压保护需求修改电路,以MAX6495-MAX6499/MAX6397/MAX6398过压保护器件为例进行说明.     

电子镇流器过压过流保护电路

电子日光灯由于其节电率高、低压启动无频闪等优点而得到广泛应用,但其在可靠性方面存在的缺陷也不容忽视。由于它工作在高频,电子镇流器中的开关振荡管较容易损坏,尤其是在电路处于过流或过压状态下极易损坏,这样的麻烦自不必提。若对电子镇流器提供可靠的保护,则日光灯在这两种异常情况下均会安然无恙。本文介绍的这个过压、过流双重保护电路能     

家用电器过／欠压保护电路

现代家庭都备有多种电器和电子设备如电视机、电冰箱、音响系统、A／V系统、微波炉和UPS系统。这些设备大都用交流电网供电，但交流电网的电压时常波动，这些电器设备只有在一定的电网电压范围内才能正常工作，偏离正常电压太远会影响电器的性能甚至造成永久性损坏。     

提供过电流和过电压保护的断路器

图1中的断路器仅需几个廉价的元件,即可对过电流和过电压故障状态进行反应.电路的核心是可调节的精密分路电压调节器D2,置在一只3引脚的封装中,提供了电压参考、比较器和集电极开路输出.     

Rail-to-rail BiCMOS operational amplifier using input signal adapters with floating outputs

An operational amplifier with rail-to-rail input and output voltage range in 0.6 μm BiCMOS technology is presented. Two simple input signal adapters with floating outputs serving as pre-stages are introduced. They are followed by a differential amplifier. The adapters translate the input signals into a floating level within the operating region of the differential amplifier, enabling rail-to-rail operation. An inverter-based simple rail-to-rail class AB output stage has been used. With a single supply of 1.5 V, the proposed rail-to-rail operational amplifier achieves 72 dB DC open-loop gain, 2.54 MHz unity-gain frequency, 62° phase margin, 2.5 V/μs slew rate, and 147 μW power consumption.     

把DAC的输出从单端模式转换到差分模式的电路

高速DAC,比如模拟器件(AnalogDevices)公司的AD9776/78/79TxDAC系列,能提供差分输出,但对于低端交流电应用或高精度电平设置应用,配备差分转换电路的单端电流输出DAC提供了一种新颖的方法来生成差分波形控制功能。图1中的基本电路组合了电流输出DAC(即IC1,如8位AD5424D A C)和一个单端至差分运算放大级IC2、IC3A、IC3B——来产生要求的输出。对于双电源应用,可选择DAC的单极工作模式来达到DAC的最优性能。DAC利用单一运算放大器提供了双象限倍增或单极输出电压摆动。DAC的输出需要缓冲器,这是因为对施加到DAC输入端的代…     

40-GHz transimpedance amplifier with differential outputs using InP-InGaAs heterojunction bipolar transistors

High-gain and high-bandwidth transimpedance amplifiers (TIAs) are required for fiber-optic receiver modules. This paper reports on the design, fabrication, and characterization of a 40-Gb/s TIA for SONET/SDH STS-768/STM-256 applications based on an InP-InGaAs single heterojunction bipolar transistor (SHBT) process developed at Vitesse Semiconductor Corporation (Vitesse Indium Phosphide Release 1 or VIP-1). This amplifier consists of a single-ended input transimpedance pre-amplifier and a differential output post-amplifier. The measured differential transimpedance is 1800 /spl Omega/ with -3-dB bandwidth greater than 40 GHz. The high gain of this circuit eliminates the need for a standalone limiting amplifier between the conventional transimpedance pre-amplifier and the demultiplexer in short-reach applications.     

改进型折叠式共源共栅运算放大器电路的设计

在套筒式共源共栅、折叠式共源共栅运放中,折叠式共源共栅运算放大器凭借较大的输出摆幅和偏置电压的较低等优点而得到广泛运用。但是,折叠式的这些优势是以牺牲较大的功耗、较低的电流利用率而换取的。本文以提高电流利用率为着手点设计了一种改进的折叠式共源共栅运算放大器,在相同的电压和负载下改进的折叠式共源共栅运算放大器能显著提升跨导、压摆率和噪声性能。仿真结果表明在相同功耗和面积的条件下,改进的折叠式共源共栅运算放大器的单位增益带宽和压摆率是折叠式共源共栅运放的3倍。     

Circuit modeling of quantum dot semiconductor optical amplifier

A circuit model of a quantum dot semiconductor optical amplifier is proposed by employing standard rate equations. Using this model, the saturation property and dynamic performance of the quantum dot semiconductor optical amplifier are analyzed by PSPICE simulation. We also investigate wavelength conversion based on cross-gain modulation for the quantum dot semiconductor optical amplifier. The corresponding results are in agreement with the previous published works.     

为网络选择过压保护器

为了保护更高速度的信号传输的完整性,设计者可以选择不会增加容性负载的电路保护器     

防止电源电压瞬变的串联保护电路

低压电源线上的瞬变电压幅值有时能达到标称电压的许多倍。这种情况常常要求对设备保护防止有人使用不适当的功率电平。防止敏感电路过电压的常用方法是增加并联嵌位电路，保险丝或其他限流器件处于这些嵌位电路的高能吸收能力之前，其他情况由于难以安装或更换保险丝，工作环境不可接近或者需要不间断工作而要求使用高压串联保护电路（而不是并联嵌们电路）。     

Security guards: issues and approaches

The issue of security, which is considered to be the final hurdle to be overcome in achieving interoperability of US Army computer systems, is discussed. In particular, the problem of transferring data across security boundaries is examined. The primary concern is to defend against unauthorized disclosure of high-side (e.g. top secret) data to low-side (e.g. secret) users. This might be caused by high-side errors, by malicious high-side software, or by active penetration from the low side. Other concerns include defending against modification or destruction of high-side data as well as denial of service to high-side users. Typical current solutions are described. The use of a security guard (also known as a security filter), i.e. a device or set of controls that mediates data transfers across security boundaries, to prevent leakage and penetration is examined. Lessons from past failures with guards and experience with an operational guard are discussed. Although military applications are addressed, the security issues raised are also thought to apply in the commercial sector     

Semiconductor optical amplifier gain anisotropy: confinement factor against material gain

It is shown that different TE/TM mode confinement factors in a bulk semiconductor optical amplifier could not be the main reason for the gain anisotropy. Instead, the intrinsic material gain difference for TE/TM polarised light can well account for this anisotropy and its dependence on pump current.